Fluorine-containing polymers and preparation thereof



April 13, 1965' E. 5. L0 3,173,399

FLUORINE'CONTAINING POLYMERS AND PREPARATION THEREOF Filed Aug. 10. 1961I Q I Q v I g R I g Q i k E E I a Q I g I I I I I I I I l I I g g g I(24) wavy/v07; avg/9943a) Q/Sd ram-z! AWE/v02 United States Patent3,178,399 FLUGRINE-CONTAINING POLYMERS AND PREPARATIGN THEREOF ElizabethS. Lo, Poughkeepsie, N.Y., assignor to Minnesota Mining andManufacturing Company, St. Paul,

Minn, a corporation of Delaware Filed Aug. 10, 1961, SenNo, 130,670

Claims. (Cl. 20--87.7)

This invention relates to new and useful fluorine-containing polymericcompositions having improved properties and to a method for thepreparation thereof. In one aspect, this invention relates to new andvaluable high molecular weight fluorine-containing crystallinethermoplastics and partially crystalline polymers having improvedproperties. In another aspect this invention relates to a process forthe production of these new and valuable high molecular weightfluorine-containing polymers.

This application is a continuation-impart of my prior and copendingapplication, Serial No. 537,886, filed September 3.0, 1955, nowabandoned.

As an accumulative group, fluorine-containing polymeric compositionsofifer wide utility in various industrial applications due to thedesirable properties which they possess such as good physical andchemical stability. One of the most useful polymers in this field is thehigh molecular weight thermoplastic homopolymer of.trifluorochloroethylene which .possesses excellent chemical inertness,exhibits flexibility and resilience and is not alfected by water, or byhumidity, and in general, is an efiicient insulating material. At thesame time, however, certain of the other properties of the highlyfiuorinated resinous thermoplastic materials (for example,polytetrafluoroethylene and polytrifluorochloroethylene), such as theirinsolubility in organic solvents at room temperature, re- .quires thatsuch polymers be used in the form of special dispersions when applyingthem, for example, as protective coatings, and that even then, a fusiontechniqueis often necessary in order to form a continuous coating orfilm of the polymer. Further, the techniques presently employed formolding polytrifiuorochloroethylene thermoplastic, for example, requirethe use of high tempera- :tures ranging between about 415 F. and about625 R,

which temperatures are often necessary in order to cause the polymer toflow readily. Such temperatures, however, may also cause undesirabledegradation of the polymer.

In addition .to the desirability of having a fluorine-containingthermoplastic having improved properties, there also has been a demandfor asynthetic resin which possesses a combination of chemical inertnessto strong and corrosive chemicalssuch as fuming nitric acid, inertnessto aromatic and aliphatic oils and fuels, and especially inertness toswell ,by hydraulic ester-type fuels, high tensile strength, retentionof reversible elongation properties over a wide range oftemperatures.-that is, from temperatures .of about -30 :F. to about 600F.--solubility in relatively volatile organic solvents and vehicles, andwhich is easily vulcanized and fabricated into a wide variety ofarticles.

It is therefore an object of the present invention to provide new andvaluable fluorine-containing polymeric materials having improvedproperties, and to provide a method for the manufacture thereof.

Another object of this inventionisto providenew fluorine containingpolymers which can be molded into a variety ;of useful end products attemperatures which are below that at which degradation ordiscolorationof the polymer occurs.

Another object is ;to provide new resinous thermoplastic .materialssuitable as coatings or films having desirable physical and chemicalcharacteristics, exhibiting ice various powerful reagents, and at thesame time possessing relatively high hardness and flexibility over awide range of temperatures and which are soluble in various solvents andother vehicles at room temperature.

Another object is to provide a synthetic high molecular weight partiallycrystalline resin having good reversible elongation, which is easilyvulcanized and which retains its flexibility when exposed to lowtemperatures, and which is resistant to degradation and hardening attemperatures up to 600 F.

Another object is to provide a synthetic high molecular weight and onlypartially crystalline polymeric material which is resistant to strongand corrosive chemicals such as fuming nitric acid and to aromatic,aliphatic and estertype fuels and which has good physical and mechanicalproperties, including high modulus, high tensile strength and reversibleelongation.

A further object is to provide a fluorine-containing polymer which isreadily applied as a protective coating to surfaces which are to beexposed to strong chemicals or corrosive fuels.

A further object is to provide a high molecular weight partiallycrystalline fluorine-containing resin having a combination of the aboveproperties and which is readily fabricated into a wide variety of usefulend products.

A still further object is to provide a process for the manufactureoftluorine-containing polymers having the above-mentioned desirablecharacteristics.

Various other objects and advantages of .the present invention willbecome apparent to .those skilled in the art from the accompanyingdescription and disclosure.

Accordingly, these objects are accomplished by the novel processwhichcomprises copolymerizing hexailuoropropene and vinylidene fluoridein the presence of a polymerization promoter. Best results are obtainedby conducting the polymerization process of the present invention in anaqueous emulsion polymerization system. The presently described processis generally carried out either under autogenous or constant pressureand at a temperature between about 0 C. and about 100 C. The polymersthereby obtained are valuable macromolecules which are adaptable to anumber of commercial uses ibasedon the fact .that their variousproperties range from those of rigid resinous thermoplastics .to tough,high tensile rubber-like materials possessing varying degrees .offlexibility, elasticity and extensibility, and which are readilyvulcanized and processed. The copolymers of hexafiuoropropene andvinylidene fluoride of the present invention are particularlyoutstanding and unique with regard to their remarkable high temperatureproperties and excellent resistance to powerful and corrosive chemicalssuch as fuming nitric acid and aromatic, aliphatic and ester-type oils,fuels and lubricants in general.

The copolymers of the present invention contain hexafluoropropene .(oromegarhydroperfiuoropropene) and vinylidene fluoride in varyingcomonomer ratiosfrom about one to about mol percent, preferably fromabout one to about 13 mol percent. The particular composition of thepolymer product obtained in any particular copolymerization reaction ofthese two monomers depends to a large extent-uponthe composition of themonomer mixtureinitially charged to the reaction zone and the reactionconditions employed to effect copolymerization. In carrying out thepolymerization reaction is has been found that the copolymers havingabove about 15 mol percent of hexailuoropropene .are essentiallycompletely amorphous elastomers and are particularly outstanding fortheir low torsional modulus and retention of their rubbery propertiesover a wi-derange of tem peratures, i.e. between about F. andabout 600F. without embrittlement,

degradation or hardening. Those copolymers containing between about 6and about 15, preferably between about 6 and about 14, mol percent ofcombined hexafluoropropene are partially crystalline thermoplasticresins with outstanding high tensile and reversible elongationproperties. Those copolymers having between about 1 and about 3 molpercent of hexafluoropropene are normally resinous thermoplasticmaterials at room temperature and also retain their flexibility over awide range of temperature without embrittlement. Those copolymerscontaining between about 4 and about 6 mol percent of combinedhexafluoro- :propene are valuable resinous thermoplastic materialshaving slightly rubbery characteristics.

The copolymers of the present invention are prepared by employing aninitial monomer charge or feed stock containing between about 5 andabout 20 mol percent of hexafluoropropene (oromega-hydroperfluonopropene), the remaining major constituent of themonomer charge being vinylidene fluoride. An initial monomer chargecontaining between about 5 and about mol percent of hexafluoropropene,or less than about 20 weight percent of hexafluoropropene based on thecombined total weight of hexafluoropropene and vinylidene fluoride inthe monomer charge, leads to the production of resinous thermoplasticmaterials having between about 1 and about 6 mol percent of combinedhexafluoropropene, some of which, as above indicated, have slightlyrubbery characteristics. When an initial monomer charge containingbetween about 10 and about 20 mol percent of hexafiuoropropene, orbetween about 20 and 30 weight percent of hexafluoropropene, isemployed, the harder and less snappy thermoplastic resins with unusuallyhigh tensile properties and reversible elongation are obtained, that is,those containing between about 6 and about mol percent of combinedhexafluoropropene, the remaining major constituent being vinylidenefluoride.

It is within the scope of the present invention to include in themonomer charge of hexafluoropropene and vinylidone fluoride, a minorproportion, usually less than about 15 mol percent, of a third monomerwhich is preferably a polymerizable ethylenically-unsaturatedhalogensubstituted organic compound such as fluoro-l,3-dienes (e.g.1,1,3-trifluorobutadiene) and halogen-substituted vinyl and allyl alkylethers (e.g. l,l,2,2-tetrafluoroethyl vinyl ether and2,2,2-trifluoroethyl allyl ether) to produce useful terpolymers. Thepresence of a third monomer improves the low temperature flexibility ofthe polymer without significantly sacrificing any of the desirableproperties of the hexafluoropropene-vinylidene fluoride polymers of thepresent invention.

As indicated above, the copolymerization reaction betweenhexafluoropropene and vinylidene fluoride is carried out in the presenceof a polymerization promoter which may be a free radical-forming or anionic-type promoter. The free radical-forming promoters or initiatorscomprise the organic and inorganic peroxy and azo compounds. The ionicinitiators comprise inorganic halides of the Friedel-Crafts catalysttype, and mineral acids. The initiator is genreally employed in anamount between about 0.001 and about five parts by weight per 100 partsof total monomers employed, and preferably are employed in an amount ofbetween about 0.01 and about 1.0 part by weight.

The polymerization catalyst system may be aqueous or non-aqueous. Of theaqueous systems the emulsion polymerization systems are preferred sincesuch systems lead to good yields of high molecular weight copolymers ofhexafiuoropropene and vinylidene fluoride having the desirableproperties herein described. Activators, accelerators and bufiers alsomay be included as ingredients of the aqueous systems, as desired.

The different types of aqueous emulsion systems may be convenientlydifferentiated on the basis of the promoter employed to initiate thecopolymerization reaction. For example, one type of aqueous emulsionsystem is that in which an organic peroxide, which is preferably awatersoluble peroxide, is employed as the initiator and a second type isthat in which an inorganic peroxy compound is empolyed as the initiator.Exemplary of the organic peroxides or oxidants which are particularlypreferred as the initiators in an aqueous emulsion system are cumenehydroperoxide, diisopropyl benzene hydroperoxide, tri isopropyl benzenehydroperoxide, tertiary-butyl hydroperoxide, tertiary-butyl lperbenzoateand methyl cyclohexane hydroperoxide.

A second type of suitable aqueous emulsion polymerization system is thatin which the promoter or initiator is one of the group of water-solubleinorganic peroxides such as the perborates, persulfates, perphosphates,:percarbonates, barium peroxide, zinc peroxide and hydrogen peroxide.Particularly effective inorganic peroxides are the water-soluble saltsof the peracids such as the sodium, potassium, calcium, barium andammonium salts of the persulfuric and perphosphoric acids such aspotassium persulfate and sodium perphosphate.

The emulsifier which is employed in the aqueous emulsion systemscomprise the inorganic derivatives derived from aliphatic carboxylicacids including both the unsubstituted hydrocarbon andhalogen-substituted aliphatic carboxylic acids. The non-halogenatedhydrocarbon type of emulsifiers or soaps comprise the metal saltderivatives such as the potassium and sodium salts derived fromhydrocarbon aliphatic acids having an optimum chain length between about14 and about 20 carbon atoms per molecule and are typically exemplifiedby potassium stearate, sodium oleate and potassium palmitate, and anymixture thereof.

The preferred emulsifiers are the halogen-substituted carboxylic acidswhich are at least half fluorinated and which have between about 4 andabout 20 carbon atoms per molecule. The particularly preferredhalogen-substituted emulsifiers are the perfluorochloroalkanoic acidshaving at least 2 fluorine atoms for every chlorine atom and theperfluoroalkanoic acids, said halogen-substituted emulsifiers havingbetween about 6 and about 14 carbon atoms per molecule. These preferredemulsifiers are produced by a variety of procedures. One procedureinvolves the potassium permanganate oxidation of a perhalogenated olefinwhich is at least half fluorinated and which is the product of thermalcracking of high molecular weight homopolymers or copolymers ofperfluoro and/ or perfluorochloroolefins. This oxidation is generallycarried out in a basic medium at a temperature which is preferably asub-zero temperature such as l0 C.

A second procedure involves treating with fuming sulfuric acid, thetelomer product obtained by telomerizing an olefin which is at leasthalf fluorinated such as trifluorochloroethylene, in the presence of abromohalomethane or a sulfuryl halide as the telogen. Such telomerproducts are prepared by reacting the olefin and telogen in the presenceof a promoter such as benzoyl peroxide at a temperature between about 75C. and about 210 C. in the presence or absence of sulfur dioxide.

When trifiuorochloroethylene is telomerized with a bromohalomethane suchas bromotrichloromethane, or with a sulfuryl halide such as sulfurylchloride, the telomeric products are represented by the followinggeneral formulae, respectively:

wherein M is a perhalomethyl radical having a total atomic weight nothigher than 146.5, 11 is an integer from 2 to 10, Y is a halogenselected from the group consisting of fluorine, chlorine and bromine,and Y is a halogen selected from the group consisting of chlorine andbromine. The hydrolysis of these telomers in fuming sulfuric acid at atemperature between about C. and about 210 C. leads to the production oforganic perfluorochlorocarboxylic acids having the recurring CF CFC1-unit .3,5,7,8-tetrachloroundecafluorooctanoic acid. Other halogenatedemulsifiers which may be used are the derivatives of the organicpolyfiuorocarboxylic acids disclosed in US. Patent No.'2,559,752 asbeing efficacious dispersing agents in polymerization reactions.

The emulsifier is generally employed in a quantity between about 0.2 andabout 10.0 parts by weight per 100 parts of total monomers charged, andpreferably between about 0.5 and 5.0 parts by weight are used.

Activators which are often used in conjunction with the peroxy compoundcomprise sodium bisulfite, sodium ,rnetabisulfite, sodium thiosulfate,sodium hydrosulfate, a

reducing sugar such as dextrose and levulose, and in general, anywaterasoluble reducing agent. Such activators are generally employed inan amount between about 0.2 and about 0.8 part by weight per 100 partsof total monomer employed.

Accelerators which may be employed in the aqueous polymerization systemscomprise Water-soluble variable .valence metal salts of sulfates,nitrates, phosphates, and

chlorides such as cuprous sulfate, ferrous sulfate and silver nitrate.Such compounds are generally employed in an amount between about 0.01and about 1.0 part per 100 .parts of total monomer employed, andpreferably in an amount between about 0.05 and 0.5 part by weight. Whenan activator suchas sodium metabisulfite, and an vaccelerator.suchasferrous sulfate, are employed, the catalyst system is referred to as aredox system. The above-mentioned organic peroxides are preferablyemployed in such a redox system.

Although the pH of the polymerization system may be between about 2 andabout .10, it has been found that :best results are obtained in anaqueous system when the hexafluoropropene and vinylidene fluoride arecopolymerized at a pH between about 4-and about 8. Appropriate pHconditions are maintained .by the addition of a buffer as an ingredientof the polymerization catalyst system.

Such buffers comprise disodium hydrogen phosphate and sodium metaborate.When .the emulsifier is charged to the polymerization zone as a freeacid such as perfluorooctanoic acid, .it is best to employ a buffer suchas disodium hydrogen phosphate and to maintain the pH of the systemwithin the preferred range, that is, between about 4 and about 8.

As indicated above, the polymerization process of the present inventionalso may be carried in a non-aqueous mass or .bulk polymerization systemcomprising a free radical-forming promoter such asthe organic peroxycompounds and azo compounds, or an ionic promoter. The organic peroxideswhich may be used include the aliphatic and aromatic peroxy compounds aswell as the fluorine and chlorine-substituted organic peroxides.Exemplary of suitable aliphatic peroxides are diacetyl peroxide, lauroylperoxide, tertiarybutyl peroxide, caprylyl peroxide, trichloroacetylperoxide, perfluoropropionyl peroxide, 3- carboxy propionyl peroxide,3,4-dibromobutyryl peroxide, trifluoroacetyl peroxide, difluoroacetylperoxide and perfluorononanoyl peroxide. Exemplary of the suitablearomatic peroxides are 'benzoyl peroxide, p-nitrobenzoyl peroxide and2,4-dichlrobenzoyl peroxide. Exemplary of the azo compounds which may beemployed are alpha, alpha-azo-isobutyronitrile, alpha,alpha-azomethylnitrile and alpha,alpha-azo-ethylnitrile. Exemplary of suitableionic initiators which may be employed in the mass type polymerizationsystem are Friedel-Crafts type catalysts such as boron trifluoride,aluminum trichloride, stannic about 160 atmospheres.

chloride, ferric chloride, titanium tetrachloride and phosphoruspentachloride; and mineral acids such as sulfuric acid and phosphoricacid.

The polymerization process of the present invention may also be effectedin the presence ofan organic solvent instead of or in addition to water.Examples of solvents of this kind are hydrocarbon solvents such ashexane, isooctane, and cyclohexane; aromatic solvents such as benzeneand toluene; oxygenated solvents such as methanol, tertiary-butanol,dioxane and tetrahydrofuran; and preferably fluorochlorocarbon solventssuch as fluorotrichloromethane (Freon-1 l As indicated previously, thecopolymerization process of the present invention is generally conductedat a temperature between about 0 C. and 100 C. Particularly goodsresults are obtained when the temperature of copolymerization ismaintained between about 25 C. and

about C. especially when the above-described prepressure which generallycorresponds approximately to the pressure exerted by the vinylidenefluoride comonomer, and, in general, this pressure does not exceedConstant pressures may also be used, particularly if the reaction isconducted in a con tinuous manner, as discussed below. Thecopolymerization of hexafiuoropropene and vinylidene fluoride also maybe effected under super imposed pressure up to about 1,000 atmospheresor higher, if desired. These extreme pressures are obtained .by the useof special high pressure equipment if necessary, and an inert gas suchas nitrogen to obtain the desired elevated pressure. The presentlydescribed copolymerization process is effected over a relatively widerange of reaction time such as between about 2 and about hours, but, ingeneral, best yields and results are obtained between about 6 and 72hours.

The polymerization reaction can be carried out in a batch-wise -orcontinuous manner as desired. In conducting the polymerization inacontinuo-us manner a mixture of the monomers is passed continuouslythrough a zone which is maintained at reaction conditions and which canbe provided with stirrers or other means of agitation. Alternatively,the catalyst can be injected into the system which is passing throughthe reaction .zone.

Plasticizers and finely divided solids which serve as filters can beincluded in the polymerization mixture and the polymerization can becarried out in their presence. Examples of suitable fillers includepigments such as titanium oxide, metals such as copper and iron powderand other finely divided materials such as mica andasbesto s. Theseandsimilar materials can also be added to the pre-formed polymers. It isalso Within the scope of the present invention to admix the copolymersofthe present invention with a thermoplastic material such as highmolecular weight polytrifiuorochloroethylene homopolymer to obtaincopolymers having improved impact strength.

The hexafiuoropropene-vinylidene fluoride copolymers of the presentinvention are suitable and useful as durable, flexible coatings forapplication to metal or fabric surfaces. The copolymers are dissolved ina suitable solvent and applied to the surfaces by spraying, brushing, orother such conventional coating techniques. Particularly useful solventsfor this purpose comprise the relatively low molecular weight andvolatile aliphatic carboxylic acid esters such as methyl acetate, ethylacetate and-butyl acetate. It has been found that the copolymers of thepresent invention are only partially soluble in organic ketones such asacetone, methyl ethyl ketone and isobutyl' finished polymers of thepresent invention in order to obtain greater solubility in the morevolatile organic solvents such asthe ketones and to obtain increasedsoftness in the rubbery characteristics which may sometimes be de- 50 C.under autogenous pressure with continuous shaking of the bomb. At theend of the 24 hours the bomb was vented to atmospheric pressure toremove the unreacted monomers. The polymer latex was coagulated sirable.The polymerization reactions which are carried by freezing it at liquidnitrogen temperature. The coaguout in the presence of the polymerizationpromoters of lated product was collected, washed thoroughly with hot thepresent invention normally tend to form very high water to removeresidual salts and dried in vacuo at a molecular weight copolymerproducts of hexafluoroprotemperature of 35 C. A white resinousthermoplastic pene and vinylidene fluoride, that is polymers having awas obtained which was very slightly rubbery, and was molecular weightof at least 50,000. A reduction of the obtained in a 58 percentconversion. This product was strength of the recipe or polymerizationpromoter merely analyzed and was found to contain 61.3 percent fluorineslows the rate of reaction without appreciably affecting correspondingto 5 mol percent of combined hexafluorothe molecular weight of thefinished copolymer. It has P p and 95 mol Percent Of combinedvinylidfihe been found, however that the addition of variouspolymerifluoride. Upon analysis for carbon content, the product zationmodifiers appreciably reduces the molecular weight Was Shown to contain35.48 percent carbon corresponding of the copolymer products andincreases their solubility 0 6 H 01 P r nt f Combined hexafluoropropeneand without affecting unduly the over-all yield. Suitable 9 m l per n ofcomb n v nyl n fl r Th polymerization modifiers include chloroform,1,1,2-tri- W ig P of Combined hexafihoropfopehe andchlorotritluoroethane (Freon-113), carbon tetrachloride, vinylidenefluoride, based uP011 the Carbon analysis, was bromotriehloromethane,trichloroacetyl chloride and found to h6 13 and 87 Wfiight Percent, p'y- Y dodecyl mercaptan. These polymerization modifiers are analysis Ofthis Product Shows it to be highly Crystalhhhpreferably added in amountsbetween about 1 and about This y g y y hexafluoropmpehe-vinyli- 10 partsby weight per 100 parts of total hexafiuoroprodene fluoride copolymerwhen milled in a rubber mill pene and vinylidene fluoride charged to thepolymerizaat C. yi a hoh-tlahsparhht Plastic Sheetwhen ti Zone, 25pressed between chrome-plated ferrotype plates in an The followingexamples are offered a a better undep. electrically-heated Carver pressat 325 F. for a period of standing of the present invention and are notto be con- 5 minutes at 10,900 Pounds P Square inch, a Clear,flexistrued as unnecessarily limiting thereto. The Gehman hle P195ticSheet Was Obtaihfidstiffness values given in the following examples werede- The resistance of tha resinous thhrlhoplasfic copolymer t i daccording t ASTM D i ti D 1()53 49T of this example to fuels and strongcorrosive chemicals was excellent as evidenced by the fact that thecopolymer EXAMPLEl exhibited a volume swell of only 1 percent after ex-After flushing a 300 ml. aminco polymerization bomb posure at 25 C. to afuel containing 30 percent by with nitrogen, the bomb was charged withthe following volume of toluene and 70 percent by volume of isooctaneaqueous emulsion polymerization catalyst system, freezfor 4 and 7 days,and only a 4 percent volume swell after ing the contents of the bombafter the addition of each exposure at 25 C. to red fuming nitric acidfor 4 and ingredient; 7 days. (1) 15 ml. of water containing 0.3 gram ofdissolved The results of further.prefparafion f copolymers ofhexafluoropropene and vinylidene fluoride are set forth sodlummetabisulfite, T M I Th d f n d 1 d d h (2) 90 ml. of water containing0.75 gram of dissolved a d e.proce ure 0 nlcu e c argmg potassiumperfluorooctanoate, the pH having been adm i EF monomer gl of i justedto 12 by the addition of a 5 percent aqueous tions in 1cate 1n ab e I.After flus mg with nitrogen an autoclave was charged with 2700 gramswater 13.5 potasslurn hydroxide solut1on, and Cl CF CFCI CF COOH 3 5 K S0 d (3) ml. of water containng 0.75 gram of dissolved pograms 2 )3 2 1grams 2 2 8 an tassium persuliate. 45 28.8 grams Nag-IP0 The autoclavewas pressured four times with nitrogen, vented, then pumped to a 20 inchIn a separate experiment, the final pH of this polymerizamercury vacuum.Atfer heating to 64 with agitation tion catalyst system was found to beabout 7. The bomb the autoclave was pressured with the given monomer wasthen connected to a gas transfer system and evacumixture to 125 p.s.i.g.and the feed regulator was set to filed at liquid nitrogen temperature-The bomb Was then continue demand feeding at this pressure throughoutthe charged with 12.4 grams of h P pene and 47.6 reaction period. Afterthe feed cylinder pressure dropped grams of vinylidene fluoride to makep a total monomer markedly, indicating that the liquid phase wasexhausted, charge containing 10 mol percent of hexafluoropropene thepolymerization was stopped and the polymeric latex and mol percent ofvinylidene fluoride. The polyrnwas recovered. Polymer samples wereobtained by freeze erization bomb was then closed and placed in a me- 55coagulation, followed by washing with hot water, dissoluchanical shaker.The polymerization reaction was contion in acetone and represcipitationin water. Polymer ducted for a period of 24 hours at a constanttemperature properties are given in Table II.

Table 1 5. irdiifili cifaitgft. airfie d??? cfiiiitils 33351333piiiifitf g. viti sli yin i? 'r ififif 8 133? charge inn/at 64 (1.acetone 1 37 55s r 2 so 570 i1; 3 iii: a 91 582 135 2. 0 125 602 .90 34.9 so. 7 90. 7 4 93 595 4. 3 500 .88 35.8 37. 4 04. 2 5 83 36 Z 184 2. 6125 300 .80 34.2 70.8 87. a

2 IICFzCF2OFCFz was the comonomcr.

Table II Unoriented film -Mole O-FiOHz, Intrinsic Run No; Percent found1 Comonomer viscosity charged 'in acetone Tensile, Modulus, Elongap.s.i.p.s.i. tion, p.s.i.

1 Based on percent carbon analysis.

2 Modulus calculated at extension rate of 0.2 in./min.

3 Elongation based on extension rate of 2 in./min.

To illustrate the outstanding tensile and reversible elongationproperties of the partially crystalline elastomers having between about6 and about 15, particularly between about 6 and about 14, mol percentof hexafiuoropropene, the product of tensile strength and reversibleelongation is reported in FIGURE 1 for various hexafluoropropene molratios, this data being obtained by utilizing the same polymerizationtechniques as in Examples 2-6. Although the tensile strength increasedand the reversible elongation decreased with increasing amounts ofhexafluoropropene in the copolymer, those copolymers having between 6and about 14 mol percent of hexafluoropropene show both increasedtensile values and also unexpectedly good reversible elongation.Moreover, the tensile-reversible elongation product of those copolymershaving between about 1 and about 14 mol percent hexafiuoropropene isactually comparable to or higher than the highly crystalline vinylidenefluoride homopolymer. Above about 94 mol percent vinylidene fluoride(i.e. less than 6 mol percent hexafluoropropene) the copolymer isessentially crystalline in nature and the reversible elongationdecreases rapidly.

Measurement of tensile strength and reversible elongation were made on40 mil thick specimens pressed at 350400 F. and quickly cooled to roomtemperature. Elongation was measured on the sample by pulling at anextension rate of 2 inches per minute until the sample broke. The lengthof the broken sample at break and after retraction was observed, and thereversible elongation of the sample was calculated from the dataobtained.

As previously stated, the copolymers of the present invention preparedby copolymerization of omega-hydroperfluoropropene or hexafluoropropeneand vinylidene fluoride under the polymerization conditions previouslydiscussed possess unique and highly desirable physical, mechanical, andchemical properties. They have high tensile strength and good reversibleelongation and are remarkably resistant to embrittlement, degradationand discoloration at temperatures between about -30 F. and about 600 F.and higher. They are equally remarkably resistant to swell by aromaticand aliphatic oils and fuels, and ester-type hydraulic fuels such asrelatively high molecular weight alkyl esters of organic dicarboxylicacids having typical oily characteristics. In addition they areresistant to swell and chemical break-down when exposed to strongpowerful corrosive agents such as red fuming nitric acid and ozone. Inaddition, they do not swell when exposed to carbon bisulfide, carbontetrachloride, 2,S-dichlorobenzotrifluoride, diethyl ether and arestable to attack by sunlight, fungi and micro-organisms in general.

The hexafluoropropene-vinylidene copolymers of the present invention areparticularly suited as durable, flexible coatings to various fabric,metallic, and other rigid surfaces. They are especially valuable asinsulating materials for motor parts, wires and the like. The resinouscopolymers, that is those containing between about 1 and about 6 molpercent of hexafluoropropene, are used in a preferred form as coatingsor laminates for metal surfaces employed in the manufacture of aircraftcomponent parts such as aluminum surfaces of tanks and other componentparts exposed to strong reagents. They also may take the form ofprotective envelopes and other articles of manufacture which arecomprised of exposed surfaces which may be exposed to abrasion or otherforms of impact in the course of forming their function under specialenvironmental conditions.

The partially crystalline, high tensile strength copolymers containingbetween about 6 and about 15, particularly between about 6 and about 14,mol percent of hexafiuoropropene (or omega-hydroperfluoropropene) areextremely useful because of their unique combination of high tensilestrength and reversible elongation properties and are especiallysuitable as durable, flexible coatings for application to various fabricsurfaces. These surfaces may, in a preferred form of application, takethe form of protective clothing (for example, as suits, boots, gloves,helmets and other wearing apparel) and other articles of manufacturewhich are comprised of exposed surfaces which may be subjected tobending, folding, or other forms of distortion in the course ofperforming their function under special environmental conditions. Theymay also be used in film form (either oriented or unoriented) e.g.' inelectrical tapes, magnetic recording tapes, etc., and as protectivecoatings on tanks, storage vessels and the like.

The hexafluoropropene-vinylidene fluoride copolymers of the presentinvention are moldable into various articles of manufacture bycompression molding at temperatures between about 250 and about 400 F.,and at a pressure of 1500 to 3000 pounds per square inch in about 5 to20 minutes. These copolymers may also be extrusion-molded at about 300F. and also may be molded by conventional transfer molding techniques.

As is apparent, the present invention relates to valuable novelcrystalline thermoplastic and partially crystalline thermoplasticpolymers comprising hexafiuoropropene and vinylidene fluoride, and to amethod of preparation of such polymers in various comonomer ratios.

Various alterations and modifications of the polymerization systememployed and reaction conditions may become apparent to those skilled inthe art without departing from the scope of this invention.

I claim:

1. A novel thermoplastic and at least partially crystalline copolymerconsisting essentially of between 87 and 99 mol percent vinylidenefluoride and between 1 and 13 mol percent of a member selected from thegroup consisting of hexafluoropropene and omega-hydroperfiuoropropene,the product of the tensile strength (p.s.i.g.) and percent reversibleelongation of said copolymer being at least 1,000,000.

2. A novel resinous crystalline thermoplastic copolymer consistingessentially of from 1 to 6 mol percent of hexafiuoropropene and from 94to 99 mol percent of vinylidene fluoride, the product of the tensilestrength (p.s.i.g.) and percent reversible elongation of said copolymerbeing at least 1,000,000.

3. The novel resinous crystalline thermoplastic copolymer of claim 2having about 5 mol percent hexafluoropropene.

4. A novel thermoplastic and partially crystalline co- 1 1' 1 Z polymerconsisting essentially of from 6 to 13 mol percent References Cited bythe Examiner hexafluoropropene and from 87 to 94 mol percent vinylidenefluoride, the product of the tensile strength (p.s.i.g.) UNITED STATESPATENTS and percent reversible elongation being at least 1,000,000.2,435,537 2/48 Ford et al, 260-921 5. A novel thermoplastic andpartially crystalline co- 5 3,051,677 4/57 Rexford 260-87.7

polymer consisting essentially of from 6 to 13 mol percentomega-hydroperfluoropropene and from 87 to 94 WILLIAM SHORT, PrimmyExaminer,

mol percent vinylidene fluoride, the product of the tensile strength(p.s.i.g.) and percent reversible elongation be I BURSTEIN, LIBERMAN,Examinersing at least 1,000,000.

1. A NOVEL THERMOPLASTIC AND AT LEAST PARTIALLY CRYSTALLINE COPOLYMERCONSISTING ESSENTIALLY OF BETWEEN 87 AND 99 MOL PERCENT VINYLIDENEFLUORIDE AND BETWEEN 1 AND 13 MOL PERCENT OF A MEMBER SELECTED FROMTHEGROUP CONSISTING OF HEXAFLUOROPROPENE AND OMEGA-HYDROPERFLUOROPROPENE,THE PRODUCT OF THE TENSILE STRENGTH (P.S.I.G.) AND PERCENT REVERSIBLEELONGATION OF SAID COPOLYMER BEING AT LEAST 1,000,000.